Spectrophotometer lamp housing



x@ 3,458,693 f if k X ff, A July 3,458,698

SPECTROPHOTOMETER LAMP HOUSING Filed April 10, 1957 2 Sheets-Sheet l July 29 1959 s. R. GILFORD ETAL 3,458,698

` SPECTROPHOTOMETER LAMP HOUSING Filed April 1o, 1967 2 sheets-sheet 2 United NStates Parent Office l 3,458,698 Patented July 29, 1969 3,458,698 SPECTROPHOTQMETER LAMP HOUSING Saul R. Gilford and Robert J. Emary, Oberlin, Ohio, as-

signors to Gilford Instrument Laboratories, Inc., Oberlin, Ohio, a corporation of Ohio Filed Apr. 16; 1967, ser. No. 629,137 Int. Cl. F21v 7/ 00; G02b 1 7/ 00; G02f 1/34 U.S. Cl. 240-41.35 15 Claims ABSTRACT OF THE DISCLOSURE A spectrophotometer lamp housing having a plurality of lamps arranged proximate to the illumination exit aperture, a pivotally mounted mirror for at any one time rellecting illumination from only one of the lamps through the exit aperture, and a plural lobed, detented cam drive for precisely pivoting the mirror through relatively imprecise cam rotations. Mounted on the same drive shaft as the plural, lobed ca'm and driven synchronously with the cam is a circular sivitch plate having a detent thereiny cooperating with switch contact buttons for energizing the lamps.

This invention relates -generally to an improved spectrophotometer lamp lhousing having a plurality of lamps,

the illumination of only one of which is to be transmitted at any one tiriie, and more particularly to such lamp housing having a mirror -pivotally driven to a precise different angular, location associated with each of the lamps, the mirror. drive and lamp actuating means being connected to a plural lobed cam drive.

The value` of spectfrophotometric analysis has been long recognized by research and industry. Also recognized for some time is the" increased performance provided by spectrophotometers; having two or more illuminating lamps operating at different wavelen-gths, or the like. More recently, analyzing ysystemshavebeen developed with which a plurality of test samples are repeatedly and cyclically brought within-the purview of the single beam of illumination from spectrophotometer. To maximize the accuracy of suchrsy'stems, it is necessary for the illumination from the .spectrophotometer to be precisely the same each time a'particular test sample is cyclically presented for analysis.

This precise control over the illumination from a spectrophotometer is made most diflicult when it contains a plurality of illuminating lamps; for then, the lamps must would be through the use of optics, which at any one time channels the illumination from only one of a plurality of tixedly positioned lamps out through the exit aperture of the spectrophotometer.

To the extent that prior syster'ris have provided such iilumination control, there appears to be a direct correlation between precision, complexity, size and cost. The .present invention seeks'to reverse this situation by'providing a high degree of precision in a relatively simple,

small, and inexpensive control apparatus employing a pivotal mirror which is precisely positioned by a detented plural lobed cam drive which also controls the timing of the ignition of each of the plurality of lamps.

Accordingly, a primary object of this invention is the precise control over the illumination from a spectrophotometer having a plurality of lamps.

Another object ofjthis invention is the precise regulation of a simple opticsystem for a spectrophotometer.

A further object of this invention is the synchronization of the ignition of each of a plurality of lamps within a spectrophotometer with'uthe precise associated positioningof a rellective optic means.

Yet another object of 'this invention is the incorporation within a spectrophotometer of an electromechanical drive coupled to both the lamp ignition circuit as well as the mechanical linkage controlling the pivotal position of a mirror aligned with the exit aperture of the spectrophotometer.

Other features and objects of this invention will become apparent `by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a top plan view of a spectrophotometer lamp housing according to this invention and shown in a rst driven position;

FIG. 2 is a side elevation of the interior of apparatus illustrated in FIG. l taken `along the line 2 2;

FIG. 3 is a side elevati'n of the apparatus illustrated in FIG. 1 taken along the line 3 3;

FIG. 4 is a fragmentary top view of the cam and cam follower portions of the apparatus shown in a second driven position; and

FIG. 5 is a fragmentary side elevational view of the lamp ignition control elements, shown also in the second driven position.

As shown in the top plane view of FIG. 1, there is a spectrophotometer lamp housing indicated generally by the reference number 11. The housing 11 comprises a generally rectangular enclosure 13 having an illumination exit aperture 15. A plurality of lamps 17 and 19 are physically and electrically mounted within the enclosure 13 generally proximate to the exit aperture 15. For simplicity of illustration and description only two lamps will belconsidered;H however, it will become apparent that apparatus according to this invention could accommodate many more'lamps.

A pivotally positionable mirror structure 21 is secured to the walls of the enclosure opposite to the exit aperture 15. The major elements of the mirror structure are a concave mirror 2,3, a mirror support 25 pivotal about an axle 27, and a cam follower 29 fixed to the axle for rotation thereof. The physical and geometric relationships of these elements of the mirror structure 21 are further clarified by FIGS. 2 and 35, which also illustrate various unnumbered fastening and adjusting elements of conventional nature. A biasing spring31 is secured to both the cam follower 29 and afportion of the mirror structure 21, which is fixed to a w'fall of the enclosure 13, such that the came follower, espcially its cam coacting leading end 33, and hence the mirror 13 -are urged counterclockwisg as viewed from FIG. 1. n

Afcam 35 is mounted generally parallel to the axle 27 and at right angle `to the mirror 23. As illustrated in FIG. 3, the cam 35 has two operating surfaces or lobes '37 and 39. Each of the operating surfaces has a uniform continuous radius, the two radii being significantly different-that of the surface 39 4being the shorter. As shown, the operatingsurface 39 is inclined rearwardly from the ,otherwise planar face of that element 35. Thus, as shown respectively in FIGS. 1 and 4, the cam followers coacting Iend 33 is substantially perpendicular to the operating surfaces 39 and 37r when in both the rst and second driven positions. Accordingly, the precise amount of throw of the cam follower can be calibrated exactingly.

by the shaft 41 such that both the circular switch plate and the plural lobed cam are driven synchronously. As shown in both FIGS. 3 and 5, the periphery of switch plate 45 contains a detent 47;- in the form of a triangular notch. A pair of biased rollers 49 and 51 ride over the rotating periphery of the switch plate. The roller 49 is urged by its bias arm 53 into the detent 47 when the cam operating surface 39 has positioned the cam follower end 33- into 'its first position, as shown in FIG, 3. Similarly, the roller 51, via its bias arm 55, isplaced into the detent 47 once each time that the lobe 37 forces the cam follower 29 in its most clockwise or second position, as shown in FIGS. 4 and 5 The rollers 49 and 51 form the armature ends of a pair of microswitches 57 and 59. Switch contact buttons 61 and 63 are respectively housed in and biased outwardly from the microswitches 57 and 59 so as to be mechanically translated by the coaction ofthe detent 47 and the rollers 49 and 51. By electrical circuitry not illustrated, the microswitch 57 controls the energization of the lamp 17 and, similarly, the lamp 19 and microswitch 49 are assocated. Thus, as shown in FIG. 3, the roller 49 is biased by its arm 53 into the detent 47 such that the arm 53 is sufiiciently removed from the contact button 61 for the button to translate into the lamp 17 energizing position. FIG. 5 illustrates the same relationship for the elements 47, 51, 55, and 63 for energization of the lamp 19.

Quite clearly, only one microswitch can be energized at any one time, since there is only one detent 47. Evident, from the fact that both the cam 35 and switch plate 45 are synchronously driven on the common shaft 41, is the direct relationship between the angular position of the hand knob 43 and the cam follower 29 to the state of the switches 57 and 59 and the pivotal correlation of the mirror 23 and hence reection through the aperture 15 of light from only the lamp then ignited, 17 or 19. Also evident is the ability of this apparatus to control more than two lamps by the adding of a microswitch and a cam lobe for each new lamp.

Of overriding significance to this invention is the fact that a precise amount of pivoting of the cam follower 29 and the resultant ignition and reflection of a particular lamp is accomplished by an imprecise relationship of the rollers 49 and 50, the detent 47, the switch plate 45, and the cam 35. This is feasible because of the constant yet different radii of rotation of each of the lobes 37 and 39 each of which provides a precisely fixed positioning of the cam follower 29 throughout many degrees of rotation of the cam 3S. If, for example, the lobe 39 extends for 90 of rotation of the cam, then, the mirror 23 would be in its first position to precisely refiect the illumination from the lamp 17 at all points along this 90 of rotation. Accordingly, as long as the detent 47 and the roller 49 are orientated to mutually coact anywhere within this 90, the highly desired result is achieved,

The operation of the subject lamp housing 11 is quite simple once each position of the cam follower 29 is preadjusted with relation .to the positionof the mirror 23 such that the mirror reflects, to the aperture 15, incident light from a different particular lamp for each different cam follower pivotal position. Thereafter, assuming electrical power is being supplied to the intercoupled lamps 17, 19, (etc.) and microswitches 57, 59 (etc.) rotation of the hand knob 43, such that one of the rollers 49 or 51 (etc.) latches into the detent 47,.is all that is necessary for the lamp associated with that roller to be ignited at a time that the mirror 23 is preciselyv positioned or repositioned to reflect its illumination out from the enclosure 13 via the aperture 15. A further rotation of the knob 43 brings another roller into the detent 47 and enables an associated lamp to have a precise amount of its reflection directed out from the lamp housing 11. Each and every time that a particular roller latches into the detent, the cam 35 has moved through several degrees of rotation of the same radius from the same lobe (37 or 39, etc.) and drives the cam follower 29 exactly the same distance correspond- 4 ing to repeatedly the same precise pivotal position ofthe mirror 23. Even if the microswitches, the switch platev45, and the cam 35 become misaligned by a 4fevtdegrees, the throw of the cam follower will nef be altered, since it is constant over a relatively large segment of each of the lobes of the cam.

It is believed that the invention described to reside within the embodied apparatus has been fully explained to enable those skilled in the art to fully comprehend its teachings. Clearly, the structure of the invention is capable of appreciable variation without there arising a departure from the spirit or scope ot'githe invention.

What is desired to be secured by, Letters Patent is:

1. A spectrophotometer lamp housing comprising:

an enclosure having an illumination exit aperture,-

a plurality of lamps within said enclosure, each lamp being separately ignitable, Y i

a like plurality of switches each electrically associated with only one of saidlamps, t*

detent means positioned for coactin with said switches for the discrete ignition of s aid lamps,

cam means having a plurality of lobes of different radius each associated with a different one of said lamps and each extending over a significant amount of cam surface,

a cam follower driven by said eem means,

a mirror positioned by said can'follower into as many discrete and precise locations as there are lobes, each discrete location having an angular relationship with said exit aperture and a one of said lamps.

2. The housing defined in claim 1 wherein said lamps are fixedly positioned between said exit aperture and said mirror while leaving clear a path for the reflected illumination from said mirror to said aperture.

3. The housing defined in claim 2 wherein l an axle is mounted in said enclosure remote from said aperture and said cam follower and said mirror are supported for common motion about seid axle.

4. The housing defined in claini 3 wherein biasing means continuously urges said cam follower and said mirror to follow said cam.

5. The housing defined in claim 4 wherein said axle, said mirror, said cam means and said detent means have surfaces the major portions of which lie parallel to one another and said cam follower is driven through an arc which lies in a plane perpendicular to said surfaces.

6. The housing defined in claim 1 wherein each said switch has a mechanically transferable armature, all of said armatures contact said detent means all of the time, and

at any one time no more than one of said armatures is transferred.'

7. The housing defined in claim 6 wherein said detent means comprises a generally circular plate having a single detent, and

said armatures are spaced around and biased against the periphery of said plate.

8. The housing defined in claim 7 in which said lamps and said switches are intereoupled to a common electrical source, and

the switches are interpositioned to selectively inhibit the ignition of said lamps.

9. The housing defined in claim 1 wherein common drive means synchronously couples said cam meansy to said detent means.

10. The housing defined in claim 9 wherein said cam means and said detent means are both generally planar and circular and each are concentrically carried on said common driven means.

11. The housing defined in claim 1 wherein said cam means is a generally circular, generally planar, unitary element.

more orthogonal with said cam follower when in. drivingly relation than if said lobe were entirely` within the plane of said cam element.

13. In a spectrophotometer lamp housing or the like having a single illumination exit aperture and a plurality of lamps, the illumination of only one of said lamps to pass through said exit aperture at any one time, exit illumination control means comprising:

a plural lobed cam, each lobe being of different radius and being associated with a different lamp,

a pivotal mirror disposed in direct line with said exit aperture and each of said lamps,

a cam follower interposed between said cam and said mirror for pivotally driving the latter through a plurality of precisely discrete positions each for direct= ing illumination from one of said lamps through said exit aperture, and

drive means for operating said cam to repeatedly cause said cam follow to coaot with said lobes 14e A housing as dened in claim 13 further comprisa plurality of switches for respectively coupling ignition energy to said lamps, and

detent means coacting with said switches for their discrete periodic enabling,

said lobes, switches and detent means mechanically and electrically interrelated such that said mirror is optically coupled with the discretely ignited lamp only during said periodic enabling.

15. A housing as deined in claim .14 in which said drive means also operates said detent means and said detent means and said cam are synchronously coaxial on said drive means.

References Cited UNITED STATES PATENTS 1,907,750 5/1933 De Iarnette 24U-46.01 2,253,174 8/1941 Furst 350--6 3,063,342 11/1962 Zeek 350-6 NORTON ANSHER, Primary Examiner R. M. SHEER, Assistant Examiner U.S. Cl. X.R. 0 6, 285 

